1. Field of the Invention
The present invention relates to a molding method of a molded surface fastener which is made from thermoplastic synthetic resin material and has coupling elements independently and continuously molded integrally on the surface of a sheet-like base member, the Surface fastener, and a molding apparatus thereof. More specifically, it relates to a molding method of a molded surface fastener which can be molded to have various sizes from a fine size to a normal size, and is suitable for various uses in many fields, and which can be molded continuously and efficiently in a single step with a simplified apparatus, a molded surface fastener obtained by the method, and a molding apparatus thereof.
2. Description of the Related Art
Conventional molded surface fasteners are manufactured by various systems. A typical example thereof is a system of manufacturing fasteners by a complete batch system with the injection molding. Another typical system is a system where a die wheel having a lot of molding cavities for coupling elements on the peripheral surface thereof, is rotated in one direction, and in the meantime, molten resin material is continuously introduced to the peripheral surface of the die wheel, so that a sheet-like base member and coupling elements are continuously and integrally molded. According to these systems, it is possible to mold coupling elements having conventionally well known various shapes such as a palm shape or a hook shape.
Furthermore, there is another system, in which a lot of approximately T-shaped extruding holes are provided in an extruding die side by side, while an extruding hole is formed for a base member and communicates with the lower end of each T-shaped extruding hole. According to this system, by simultaneously extruding molten resin from both of the extruding holes, a plurality of pieces of ribs each having an approximately T-shaped cross section are continuously molded on a surface of the sheet-like base member, and then the molten resin molding material is cooled and solidified. Next, the ribs are cut with a predetermined thickness in a direction perpendicular to a drawing direction of the ribs or at a proper angle, while the sheet-like base member is left uncut. After this cutting, the sheet-like base member is drawn in the molding direction, so that the cut coupling elements are individually separated by a desired pitch. Thus, the molded surface fastener is manufactured.
In these molding methods, for example, in the technique of continuously molding surface fasteners on the die wheel, it is difficult to mold a coupling element with a complex form because of the limitation of its shape or size, if improvement of productivity is attempted. On the other hand, if a certain option to the shape or size of the coupling element is attempted to be given, the continuous molding is difficult to achieve, or the number of steps is increased so that the productivity may be lowered. In any case, the difference between advantage and disadvantage would be remarkably large.
On the other hand, in the case of adopting a system in which the drawing processing is applied after cutting the ribs of the molten resin molding material on the surface of the sheet-like base member from the extruding die in order to give a certain option to the sectional shape of a coupling head portion, three steps of extrusion molding, rib cutting, and drawing are required. Especially, a high processing accuracy is required for the step of rib cutting, so that the considerable labor and time are also needed for the maintenance and management thereof.
The present invention is made to solve such conventional problems. Specifically, it has an object to provide a molding method of a molded surface fastener, which can continuously perform the molding with a completely new molding mechanism, and whose maintenance and management are easy, and whose productivity is high, and which has coupling elements each capable of being molded with new shapes until now and by various sizes, and a molded surface fastener obtained by the method, and a manufacturing apparatus thereof.
Such an object can be achieved by first through the third aspects of the present invention.
According to the first aspect of the present invention, there is provided a molding method of a molded surface fastener for continuously and integrally molding a sheet-like base member and a multiplicity of coupling elements, comprising the steps of: continuously extruding molten resin material from a first extruding hole extending in a width direction of a first extruding nozzle arranged on the downstream side in an extruding direction of the molten resin material via an extruding die of an extruding machine; passing the molten resin material extruded from the first extruding nozzle through a second extruding nozzle which is arranged at a front surface of the first extruding nozzle and has a second extruding hole corresponding to the first extruding hole; and relatively vibrating the first extruding nozzle and the second extruding nozzle in the width direction in such a way that the respective extruding holes facing each other mutually cross, wherein one of the first extruding hole and the second extruding hole includes a plurality of longitudinal rectangular openings arranged in the width direction, and the other extruding hole has coupling-element-molding openings arranged so as to correspond to the rectangular openings.
The most distinguishing feature of this invention is to relatively vibrating the first extruding nozzle which is arranged on the downstream side of the molten resin extruded from the extruding die of the extruding machine and has a multiplicity of openings, and the second extruding nozzle which is arranged in a freely slidable way at the front surface of the first extruding nozzle at the downstream side thereof and has a multiplicity of openings of which number corresponds to that of the openings of the first extruding hole so that the respective corresponding extruding holes may cross each other.
When the molten resin extruded from the extruding die in a sheet-like form passes through the first extruding nozzle and the second extruding nozzle which are relatively vibrating in the width direction, the molten resin is extruded through a communicating space of the first and second extruding holes by the relative vibration of the first extruding hole and the second extruding hole while sequentially moving from a tip of a coupling head portion to a stem portion of each coupling element. While the coupling elements are molded in the extruding direction, the sheet-like base member is continuously molded by the base-member-molding openings of the first extruding nozzle and the second extruding nozzle. At this time, a rising base end of the stem portion is molded integrally on the sheet-like base member.
Preferably, the first extruding hole may have the coupling-element-molding openings, and the second extruding hole may have the longitudinal rectangular openings, and a periphery of each of the longitudinal rectangular openings is formed to have a tapered surface gradually enlarged toward the downstream side in the extruding direction, and that the second extruding nozzle is vibrated on the front surface of the first extruding nozzle. Or alternatively, the first extruding hole may have the longitudinal rectangular openings, and the second extruding hole may have the coupling-element-molding openings, and a periphery of the coupling-element-molding opening is formed to have a tapered surface gradually enlarged toward the downstream side in the extruding direction, and the second extruding nozzle is vibrated at the front surface of the first extruding nozzle.
Since the periphery of the longitudinal rectangular opening of the second extruding nozzle is made to be a tapered surface gradually enlarged toward the extruding direction, or since the periphery of the coupling-element-molding opening of the second extruding nozzle is made to be a tapered surface gradually enlarged toward the extruding side, when the molten resin, which is continuously extruded from the first extruding hole of the first extruding nozzle and has a predetermined form, is sequentially blocked and released repeatedly by the second extruding hole of the vibrating second extruding nozzle, a part of a side of each coupling element already extruded by the second extruding hole of the second extruding nozzle is prevented from being crushed at the front surface thereof by the movement of the second extruding hole, so that a desired form of the coupling element can be obtained.
Further preferably, the first extruding nozzle may be in close contact with the extruding die and then the second extruding nozzle to the first extruding nozzle, so that the molten resin material can be directly extruded from the extruding machine. Further, it is preferable that the molding method further includes a step of cooling the molten resin molding material which has passed through the second extruding nozzle. Therefore, the molten resin extruded from the extruding die is extruded to the first extruding nozzle and the second extruding nozzle which are relatively vibrating in the width direction as it is, and the molten resin is extruded from the portions where the extruding holes of the two nozzles communicate, and the coupling elements are sequentially molded on the sheet-like base member as mentioned above, and thereafter, they are cooled and solidified.
Further, it is preferable that the molding method further includes steps of: extruding the molten resin material from the extruding machine on a peripheral surface of a cooling cylinder rotating in one direction so as to mold a sheet-like molten resin layer on the peripheral surface; and introducing the sheet-like molten resin layer into the first and second extruding nozzles arranged facing the cooling cylinder on a downstream side of the molten resin layer. In this case, the molten resin extruded from the extruding die in a sheet-like form is supplied to the peripheral surface of the cooling cylinder with a cooling means therein, and on the peripheral surface thereof, a sheet-like molten resin layer with a certain thickness is molded. This molten resin layer rotates along with the rotation of the cooling cylinder on the peripheral surface thereof. On the way of that rotation, the molten resin layer is supplied to the first and second extruding nozzles which are relatively vibrating in the width direction, and while being cooled, the coupling elements having a desired form are sequentially molded on the base member as mentioned above.
As mentioned above, in a case where the molten resin material from the extruding machine is extruded onto the peripheral surface of the cooling cylinder rotating in one direction so as to mold a sheet-like molten resin layer on the peripheral surface thereof, and the sheet-like molten resin layer is introduced into the first and second nozzles arranged facing to the peripheral surface of the cooling cylinder on the downstream side of the molten resin layer, the cooling of the molten resin layer is started at the time of being extruded from the extruding machine. Therefore, depending on the materials, the shrinkage may be so considerable that the form may easily be unstable. Thus, it is preferable that the molding method further including a step of molding a plurality of anchor members integrally on opposite edge portions of the sheet-like base member where the coupling elements are not molded, by anchor-member-molding cavities formed on the cooling cylinder at right and left periphery portions in the axial direction thereof. In this case, both the right and left edge portions where the anchor members are molded are cut and eliminated in the later finishing step.
Further preferably, each of the coupling-element-molding openings of one of the extruding holes may be shaped approximately like T or Y, or further a tip of each head-portion-molding openings in the coupling-element-molding openings of one of the extruding holes may be bent toward a base-member-molding opening. Furthermore, a form and size of each coupling element to be molded can be made to be uniform by making the vibration speed constant, or alternatively it is also possible to regularly change the vibration speed, in which case the projecting lengths of the coupling head portions are changed for each specified number of coupling elements arranged in the molding direction.
Alternatively, the vibration speed may be randomly changed. In this case, the projecting lengths of the coupling head portions of the coupling elements arranged in the molding direction are randomly changed. Moreover, it is also possible that at least one of the coupling-element-molding openings among a plurality of coupling-element-molding openings arranged laterally side by side, made to be different from the other coupling-element-molding openings in height. In this case, the heights of a plurality of the coupling elements which are molded and arranged in the width direction of the surface of the base member are made to be different.
According to the above mentioned molding methods of the first aspect of the present invention, the surface fasteners having special forms according to the second aspect of the present invention are continuously molded.
According to the second aspect of the present invention, there is provided a molded surface fastener having a plastic sheet base member and a multiplicity of coupling elements continuously and integrally molded, wherein each of the coupling elements has a stem portion integrally extending upwardly from a surface of the sheet base member and a coupling head portion projecting substantially forward in a molding direction from an end of the stem portion, and each pair of the coupling elements mutually adjacently arranged in the molding direction assumes a mirror symmetrical form, and each pair of the coupling elements mutually adjacently arranged in a direction perpendicular to the molding direction have coupling head portions projecting in parallel to each other.
In a conventional molded surface fastener which is manufactured such that approximately T-shaped ribs are continuously extruded integrally with a sheet-like base member by using a conventional extruding machine, and after cooling the surface fastener, only the ribs are cut by a predetermined pitch in the longitudinal direction thereof, and then, the base member is drawn in the extruding direction, so that a certain gap is made between the coupling elements obtained by cutting, each coupling head portion thereof mainly projects in a direction perpendicular to the molding direction, and furthermore the respective coupling elements adjacent in the molding direction are arranged in parallel with each other. Furthermore, in the molded surface fastener as a product, since the base member is drawn in the molding direction, the thickness of the base member is enlarged at a part of a base end of the stem portion of each coupling element, and the surface of the base member becomes in a state of a little waving in the longitudinal direction.
On the other hand, the projecting direction of the coupling head portion of the coupling element in the molded surface fastener according to the present invention, is mainly the molding direction, and furthermore, the coupling elements arranged adjacent in the molding direction assumes a mirror symmetrical form. Moreover, any particular secondary processing, which was necessary in the conventional molded surface fastener, needs not be applied to the molded surface fastener of the present invention, so that an extremely well-balanced and stable form including the base member can be obtained.
Preferably, in the coupling elements of the molded surface fastener, said certain angle may be 0xc2x0 in which case, the axes in projecting directions of the coupling head portions arranged in lines in the molding direction are on the same straight line, that is, the projecting directions of the coupling elements are on one straight line. This form of the surface fastener can be made by the molding method in which the first extruding hole has the longitudinal rectangular openings, and the second extruding hole has the coupling-element-molding openings, and a periphery of the coupling-element-molding opening is formed to have a tapered surface gradually enlarged toward the downstream side in the extruding direction, and the second extruding nozzle is vibrated at the front surface of the first extruding nozzle. Alternatively, said certain angle xcex8 may be within a range of 0xc2x0 less than xcex8xe2x89xa690xc2x0, and an axis in a projecting direction of the coupling head portion extends at said angle with respect to a straight line connecting centers of the respective stem portions, thus the respective head portions adjacently arranged in the molding direction are arranged in a zigzag manner. This form of the surface fastener can be made by the molding method in which the first extruding hole has the coupling-element-molding openings, and the second extruding hole has the longitudinal rectangular openings, and a periphery of each of the longitudinal rectangular openings is formed to have a tapered surface gradually enlarged toward the downstream side in the extruding direction, and that the second extruding nozzle is vibrated on the front surface of the first extruding nozzle.
Then, a form of each coupling element is determined by the shape of the coupling-element-molding opening of the extruding hole. Specifically, a vertical cross section of the coupling element may be approximately shaped like T, in which case an entire shape of each coupling-element-molding opening is also approximately like T. Alternatively, a vertical cross section of the coupling element may be approximately shaped like Y, in which case a shape of the coupling-element-molding opening is approximately like Y. Furthermore, a tip of each coupling head portion may be bent toward a surface of the base member. In this case, the coupling head portion may project only in one of the molding directions from the stem portion and is bent downward so as to form a so-called hook-shape, or the coupling head portion may project forward and rearward in the molding directions from the stem portion and is bent downward so as to form a palm tree-shape.
Further, it is preferable that thickness of each stem portion in the molding direction thereof and a projecting length of each coupling head portion of the coupling elements, which are mutually adjacently arranged in the molding direction, may be regularly changed in the molding direction. Or alternatively, the thickness of each stem portion in the molding direction thereof and a projecting length of each coupling head portion of the coupling elements, which are mutually adjacently arranged in the molding direction, may be randomly changed in the molding direction. In order to mold coupling elements having these forms, the vibration speed of the first and the second nozzles should be regularly or randomly changed. Furthermore, the heights of the coupling elements from the base member to the top thereof, which are mutually adjacently arranged perpendicularly to the molding direction, can be made to be different. Such a form of the surface fastener can be molded by the molding method in which at least one of the coupling-element-molding openings among a plurality of coupling-element-molding openings arranged laterally side by side, are different from the other coupling-element-molding openings in height.
The molding method and the molded surface fastener can be efficiently achieved by a molding apparatus according to the third aspect of the present invention.
According the third aspect of the present invention, there is provided a molding apparatus of a molded surface fastener for molding a sheet-like base member and a multiplicity of coupling elements integrally by continuous molding, characterized by comprising: a first extruding nozzle having a first extruding hole extending in a width direction thereof; a second extruding nozzle arranged at the front surface of the first extruding nozzle and having a second extruding hole corresponding to the first extruding hole, wherein one of the first extruding hole and second extruding hole is an extruding hole including a plurality of longitudinal rectangular openings arranged in the width direction, the other extruding hole has a plurality of coupling-element-molding openings arranged corresponding to the rectangular openings; and a vibrating means for relatively vibrating the first extruding nozzle and the second extruding nozzle in the width direction so that the corresponding extruding holes may mutually cross.
Preferably, the vibrating means may have a crank mechanism connected to the first extruding nozzle and/or the second extruding nozzle through a link. Or alternatively, the vibrating means may have a-cam contact fixed to the first extruding nozzle and/or the second extruding nozzle, and a cam with which the cam contact are in contact. Since these vibrating means are mechanical, the relative vibrating action of the first and second extruding nozzles can surely and accurately be achieved. Furthermore, each of the vibrating means may comprise a control means for changing the vibration speed, so that the vibrating action can regularly or randomly be controlled, at will.
Further, it is preferable that the first extruding hole may have the coupling-element-molding openings, and the second extruding hole may have the longitudinal rectangular openings, and the periphery of the longitudinal rectangular opening is formed to have a tapered surface gradually enlarged toward a downstream side of an extruding direction thereof, and the second extruding nozzle is connected to the vibrating means. In this case, in the coupling elements extruded from the second extruding nozzle, the axes in the projecting direction of the respective coupling head portions adjacently arranged in the molding direction have a certain angle to the straight line connecting the centers of the respective stem portions.
Alternatively, the first extruding hole may have the longitudinal rectangular openings, and the second extruding hole may have the coupling-element-molding openings, and a periphery of the coupling-element-molding opening is formed to have a tapered surface gradually enlarged toward a downstream side of an extruding direction thereof, and the second extruding nozzle is connected to the vibrating means, In this case, in the coupling elements extruded from the second extruding nozzle, the axes in the projecting direction of the multiplicity of the coupling head portions arranged in lines in the molding direction thereof are on the same straight line.
Further preferably, at least one of a plurality of coupling-element-molding openings arranged side by side laterally may be different from the other coupling-element-molding openings in height. In this case, it is possible to make the heights of some of the coupling elements adjacently arranged perpendicularly to the molding direction, different from the heights of the other coupling elements, so that they can effectively be coupled to the loops having various sizes.
In the molding apparatus for achieving the above-mentioned first molding system, the first extruding nozzle is arranged in series in a die of an extruding machine, and a cooling means for cooling molten resin molding material extruded from the second extruding nozzle, is arranged in front of the second extruding nozzle. In this case, it is efficient to adopt a cooling cylinder as the cooling means, but, of course, it may also be a cooling tank.
In the molding apparatus for achieving the above-mentioned second molding system, a cooling cylinder is in confrontation with a die of an extruding machine, and on a downstream side of a rotational direction of the cooling cylinder, the first extruding nozzle and the second extruding nozzle are arranged facing a peripheral surface of the cooling cylinder with a gap approximately equal to thickness of the base member. In this case, as mentioned above, the molten resin material from the extruding machine is extruded onto the peripheral surface of the cooling cylinder rotating in one direction, and a sheet-like molten resin layer is molded on the peripheral surface. Then, the sheet-like molten resin layer is introduced into the first and second nozzles which are arranged facing to the peripheral surface of the cooling cylinder on the downstream side of the molten resin layer. In this case, since the cooling of the molten resin layer is started at the time of being extruded from the extruding machine. Depending on the materials, the surface fastener may considerably shrinks and may easily be unstable. Therefore, it is preferable that anchor-member-molding cavities may be formed at right and left periphery portions of the cooling cylinder in the axial direction thereof, so that the anchor members can be molded along the opposite side edge portions of the molded base member, on its surface opposite to that where the coupling elements are molded.
According to the molding apparatus, various forms of coupling elements can be molded. Specifically, in case that each coupling-element-molding opening of the extruding hole is approximately shaped like T, the form of each molded coupling element is also shaped like T. In case that the coupling-element-molding opening of the extruding hole is approximately shaped like Y, an approximately Y-shaped coupling element can be molded. Furthermore, when a tip portion of a head-portion-molding opening in each coupling-element-molding openings of the extruding hole is bent toward a base-member-molding openings, the molded coupling element can be shaped like a hook which is projecting in one direction of the molding direction from the stem portion, or it can be shaped like a palm tree which is projecting forward and rearward in the molding directions.